1. Field of the Invention
The present invention relates to a zoom lens suitable for image pickup apparatuses, such as cameras, using a solid image sensor or a silver-halide film.
2. Description of the Related Art
Image taking optical systems used for image pickup apparatuses are requested to be entirely compact, be capable of image taking with a wide angle of view, have a high zoom ratio and be provided with an image stabilizing mechanism to correct (reduce) image blur generated due to camera shake caused by hand jiggling or the like.
Moreover, the image taking optical systems as zoom lenses are also requested to have a configuration in which a movement of an image stabilizing lens unit, which constitutes part of the zoom lens, in a direction orthogonal to an optical axis for correction of the image blur causes less variation of aberrations.
An inappropriate configuration of the zoom lens or a lens unit placed further on an image side than the image stabilizing lens unit increases decentering aberration when the image blur correction is performed, which deteriorates optical performance of the zoom lens.
Therefore, in order to achieve an entirely compact configuration, a wide angle of view, a high zoom ratio and high optical performance during the image blur correction, it is important to appropriately set the configuration of the entire zoom lens, the configuration of the lens unit placed further on the image side than the image stabilizing lens unit and others.
As positive-lead type zoom lenses in which a most-object side lens unit has a positive refractive power, a zoom lens is known in which a lens unit constituting part of the zoom lens is moved for the image blur correction in a direction including a directional component orthogonal to an optical axis of the zoom lens.
Japanese Patent Laid-Open No. 2010-019945 discloses a zoom lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power and a fourth lens unit having a positive refractive power. In this zoom lens, the third lens unit is divided into a lens unit having a positive refractive power and a lens unit having a negative refractive power, and image blur correction is performed by moving the negative lens unit in a direction orthogonal to an optical axis of the zoom lens.
Japanese Patent Laid-Open No. 2010-271362 discloses a zoom lens including, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power and a fifth lens unit having a positive refractive power. In this zoom lens, image blur correction is performed by moving the fourth lens unit or part thereof in a direction orthogonal to an optical axis of the zoom lens.
The configurations of the zoom lenses disclosed in Japanese Patent Laid-Open Nos. 2010-019945 and 2010-271362 are advantageous to achieve a high zoom ratio, but make it difficult to achieve an entirely compact configuration and a wide angle of view.